How to open 2 sanbox

[970509]

So, I downloaded the sandbox and I am able to open one sandbox (sandbox default box).
How can I open another sandbox.

I am using this thing to play multiclient of certain online game.
I want to open more than 2 client at the same time is it possible?

[Buster]

If I am not wrong you must register the program in order to be able to open 2 sandboxes at the same time.